Most efforts to understand how environmental carcinogens and tumor-promoting agents increase cancer risk have focused on their effects on directly exposed cells and have identified locally operating mechanisms endogenous to the exposed tissue. In the proposed study, we will verify the hypothesis that erythropoietin (EPO) and EPO receptor (EPOR) mediate physiological responses to carcinogens and tumor promoters via endocrine-like mechanisms and contribute to tumor initiation and progression. The goal of our study is to understand how carcinogenic and tumor-promoting environmental agents induce EPO and EPOR expression, whether EPOR expressed in preneoplastic cells and established tumors plays an important role in tumor formation and metastatic progression, and what molecular signals govern EPOR expression in non-erythroid EPO target cells during tumorigenesis. To achieve this goal, we will pursue the following specific aims: To determine the role of epidermal EPOR in skin carcinogenesis (Aim #1); To determine the role of melanoma- expressed EPOR in tumor growth and metastasis (Aim #2); To identify the mechanisms of EPOR induction in tumor precursors and established tumors (Aim #3). Information obtained from our study will not only advance our understanding of how etiologic agents of skin cancer increase the rate of tumor formation and malignant conversion but also shed new light on the role of endogenously produced EPO and non-erythroid EPOR in cancer development. We expect that our findings will ultimately help devise new strategies for cancer prevention and management.